Part 15 of the “What Does It All Mean?” series, a real-life reflection on living with Type 1 Diabetes, written by Dennis Goldensohn, who has lived with T1D for nearly 60 years.
By Dennis Goldensohn: T1D for nearly 60 years, advocate, and mentor
Introduction
Managing your diabetes is dependent on having information available so that you can know how well you are managing your diabetes. Over the past 50-some-odd years, technology has advanced, which gives those who are dealing with diabetes more on-demand information to make better decisions on how to manage their diabetes.
In this article, we will be looking at how the data/information from your CGM’s Ambulatory Glucose Profile (AGP) Reports can be better understood so you can obtain better results in managing your diabetes!
The following will be discussed:
- History of systems used to measure your blood glucose (BG)
- Understand what an Ambulatory Glucose Profile (AGP) Report is and define the terminology
- Compare two AGP Reports from two individuals and see what the differences are
- Why readings from a CGM are different than from a glucometer
- Review and final comments
The information in this article is for informational and educational purposes only and should not be used as medical advice. Discuss this with your healthcare professional, doctor, or endocrinologist!
History of Systems Used to Measure Your Blood Glucose (BG)
1. Glucose Urine Test Strips
In 1968, when I was diagnosed with Juvenile Diabetes, the term Juvenile Diabetes at the time referred to those who were children, which we know today is not limited to children. To test what my glucose level was, I used urine test strips.
In the picture to the left, there is a small REAGENT AREA in blue, and that would be dipped into a urine sample. The reagent area was treated with chemicals so that it could detect glucose in the urine.
When the test strip was removed, you would compare it to the chart on the container. That would tell you how high your BG was.
2. Glucometers
Glucometers were made available in the late 1970s to people living with diabetes so they could check their Blood Glucose (BG) directly from a blood sample.
In the picture to the left, a test strip would be inserted into the glucometer, and a blood sample would be applied.
The readings in early models would take anywhere from 30–45 seconds. The result would appear on the screen.
The MARD (Mean Absolute Relative Difference) was much higher than the models available today.
Nevertheless, this gave us the ability to get BG readings directly from blood, which was much more accurate than those using urine samples. It is also the GOLD STANDARD to check the accuracy of CGM readings by the end user.
3. CGM – Continuous Glucose Monitoring Technology
In 1999, the FDA (Food and Drug Administration) approved the use of CGMs for professional use. Then, in 2001, they were made available for personal use.
CGM readings are gotten from the INTERSTITIAL FLUID that is below the skin. This is represented in the picture to the left.
This is NOT a direct reading from the blood.
Readings from a CGM can “LAG” behind actual readings taken from the blood. This will be explained later in this discussion.
Eventually, CGMs were paired with AID (AUTOMATED INSULIN DELIVERY) SYSTEMS. This included Hybrid and closed-loop systems.
Readings would be taken every minute or every five minutes depending on the brand used. The readings would be recorded in real time.
As a result of recording this data, AGP (AMBULATORY GLUCOSE PROFILE) REPORTS are generated.
Understanding an Ambulatory Glucose Profile (AGP) Report and Its Terminology
The following are “Key Measurements” from an AGP Report:
TIR – Time in Range
This is a range that is selected as the targeted range that one would want their BG readings to fall into. In this example, the TIR is 70 at the low end and 180 at the upper end. In this example, the TIR is 66%, 9% below the lower limit, and 25% above the upper limit.
Average Glucose
This is a calculation based on all of the BG readings that fall into this given time frame of 14 days. The goal in this example is 154 mg/dL.
Glucose Variability
This is a calculation that is based on the BG readings for the period of 14 days. The higher the number, the more the BG readings vary. The objective is to reduce the variability. The goal is equal to or less than 36%.
GMI – Glucose Management Indicator
This is a calculation based on the BG readings for the period of 14 days in this example. This is similar to an A1C, which is gotten from a blood sample that is sent to a laboratory. If the CGM readings of the BGs are accurate, the GMI and A1C will be comparable but not necessarily the same.
Daily Glucose Profile
This indicates what your BGs are on any one day of the week. The daily profile is from midnight to midnight. This can tell you when you have highs and lows during a particular day and/or time of the day.
Comparing Two AGP Reports
Figure 1 vs. Figure 2
| Measurement | Figure 1 | Figure 2 |
|---|---|---|
| Time in Range (TIR) | 66% | 36% |
| Average Glucose | 142 | 201 |
| GMI | 6.7% | 8.1% |
| Glucose Variability | 43.6% | 45.2% |
We can see from the table to the left that Figure 1 has better measurements than Figure 2. Nevertheless, both examples have issues. Both have high rates of Variability, and the target for that is 36% or lower. Figure 2 has a High Average Glucose, and the Target should be 154 mg/dL. The GMI in Figure 2 is too high, and it should be 7% or lower.
Based on these two AGP Reports, both individuals have some issues they need to improve on. A discussion with their doctor can help make changes in their diabetes management with the objective of improving these metrics!!!!
Why Are BG Readings From a CGM Different Than From a Glucometer?
In Figure 3, CGMs get their BG readings by measuring the INTERSTITIAL FLUID beneath the skin. The sensor’s filament is in contact with the fluid, and the reading is taken from how much glucose there is in the fluid.
A glucometer, on the other hand, gets its BG readings directly from the blood sample taken.
Based on what is described above, there can be a 10-to-15-minute LAG TIME between the readings of the glucometer and the CGM.
This is represented by Figure 4, where the locomotive of the train is ahead of the last car of the train.
How Can We Tell if the CGM and Glucometer Readings Are the Same?
In the three figures above, there are arrows going in different directions: DOWN, UP, and LEVEL.
In Figures 5 and 6, the BG Level shows that it is Not Stable and is either going Higher or Lower. This is the “LAG” that was shown in Figure 3.
In Figure 7, the BG is Stable. When the CGM’s reading is stable, you can then compare it with a glucometer.
If the CGM reading is off, some models of CGMs can be calibrated within the CGM APP.
After calibrating the CGM, wait about 30 minutes and do another comparison. If it is within +/- 10% of the glucometer reading, the readings can be trusted. If not, then the CGM might be defective and needs to be changed.
What Have We Learned?
The technology that we use to test our blood glucose has evolved over many decades, and now we have real-time data and reporting that can help us manage our diabetes much better.
We discussed what an AGP Report is and what the Key Measurements are. These measurements can help you and your doctor better understand what the current state of your diabetes management is and implement interventions to obtain better outcomes.
We looked at two AGP Reports to understand that each one of us has different outcomes, and in each example, there were issues that needed to be addressed.
We compared how a CGM determines your Blood Glucose level vs. a Glucometer and why there is, at times, a difference.
Lastly, we now know when you can compare the readings on a Glucometer and a CGM when the Blood Glucose levels are stable.
I would like to thank Diapoint for the opportunity to reach out to you so we can bring value-added educational and informational information to you in the local community.
We are our own BEST ADVOCATES, and together we will make a difference to better understand diabetes and live a long, productive, and healthy life!
What Is This Series?
At Diapoint, we believe that the most powerful education comes from real people and real lives lived with diabetes.
That’s why we’re proud to introduce a new blog series by Dennis Goldensohn.
Dennis has been living with Type 1 Diabetes for nearly six decades, diagnosed at just 16 years old, and now approaching 59 years of life with T1D, without complications. His journey is not only a testament to resilience but also to what is possible with the right mindset and support.
Beyond his personal experience, Dennis brings a lifetime of dedication to service and advocacy. He spent 45 years working in aerospace manufacturing, while also volunteering with organizations such as JDF, JDRF, Breakthrough T1D, DPAC, and the Diabetes Research Institute. Today, he continues to mentor young people navigating their futures, while sharing his lived experience with diabetes to support others.
His series, “What Does It All Mean?”, is exactly what it sounds like: a reflection on life with diabetes, beyond the numbers, beyond the devices, and beyond the daily routines.
Through this series, Dennis explores:
- The realities of living with diabetes every single day,
- The misconceptions and stigma people face,
- The history and progress of diabetes care,
- The power of community, advocacy, and teamwork,
- And ultimately, what it truly means to live a full, successful life with diabetes.
This is not just education. This is perspective and lived experience.
And above all, this is reassurance that yes, you can.
